标题： 以镭盐和软金属基质为复合靶材用于质子或电子加速器生产Ac-225 显示英文标题

标题： A Composite Target of a Radium Salt and a Soft Metal Matrix for Production of Ac-225 with a Proton or Electron Accelerator

摘要： 使用质子加速器或电子加速器生产225Ac需要一个226Ra靶。由于金属镭难以操作，因此更倾向于使用镭盐作为靶材料，例如碳酸镭。通常以粉末形式提供，粉末的平均密度较低且热导率较差，从而限制了可以在靶上耗散的束流功率。本工作提出创建一种镭盐粉末与金属基体的固态混合物。尽管铝粉已在类似应用中使用，但我们建议铟粉是放射性镭盐情况下金属基体的良好选择。靶可以通过低模压形成，无需加热，从而简化了靶制备所需的热室设备。我们描述了固态混合物如何成型，测量其热导率并与模型估算值进行比较。我们计算了在不同情景下225Ac的产率。计算表明，在辐照过程中产生的铟放射性同位素在辐照后不应产生显著的处理挑战。对于所提出的靶几何形状和束流参数，热建模表明靶温将低于铟的熔点，表面的热流将是可控的。靶界面处的热阻对靶温有较大影响。使用铟粉形成混合物，占据约40%的靶体积，在24 MeV、3 kW质子束下辐照10天时，225Ac的产率为80 GBq（2 Ci），而在25 MeV、20 kW电子束下辐照10天后三次提取225Ra的产率也大致相同。 显示英文摘要

摘要： The production of 225Ac using either a proton or electron accelerator requires a target of 226Ra. Radium metal is difficult to work with and so a radium salt, such as radium carbonate, is preferred as a target material. Normally available as a powder, the average density of the powder is low and the thermal conductivity is poor, thus limiting the beam power that can be dissipated in the target. This work proposes the creation of a solid mixture of a radium salt powder with a metal matrix. Although aluminum powder has been used in similar applications, we suggest that indium powder is good choice for the metal matrix in the case of radioactive radium salts. The target can be formed with low die pressure without any need for heating, thus simplifying the hot-cell equipment needed for target preparation. We describe how the solid mixture can be formed, measure its thermal conductivity and compare the value to model estimates. We calculate the yield of 225Ac under different scenarios. Calculations show that the radioactive isotopes of indium produced during the irradiation should not produce significant handling challenges post-irradiation. For the proposed target geometry and beam parameters, thermal modelling indicates that the target temperature will be below the melting point of indium and the heat flux from the surfaces will be manageable. Thermal resistance at the target interfaces is shown to have a large effect on the target temperature. Using indium powder to form the mixture, occupying about 40 % of the target volume, we find that the yield of 225Ac is 80 GBq (2 Ci) for a 10-day irradiation with a 24 MeV, 3 kW proton beam and approximately the same for three milkings of 225Ra after a 10-day irradiation with a 25 MeV, 20 kW electron beam.